The present invention relates to connector seals of the type which are used to connect sections of pipe to holes in concrete walls such as those used in manholes and dike walls. The connector seals are designed to attach to such a hole in a concrete wall and receive a pipe penetrating through that hole to position its open end in the manhole or other fluid well. The connector seals are used to ensure that any liquid contained within the pipe and emptying into the well is tightly sealed from escaping out of the well.
Several characteristics are important when considering connector seal design. First of all, the seal should assure a watertight connection between the pipe and the concrete access well. The connector seal should also be flexible so that it can compensate for pipe loads as well as for the misalignment or deflection of either the pipe or the concrete access well. Finally, it is important for the connector seal to have a low installation cost, offer a long service life, and allow easy routine maintenance.
There are basically two known connector seals which are designed to seal directly against a hole in a concrete wall. The first such seal is the cast-in-place type which is sealed directly into the hole at the same time that the concrete wall itself is being cast. The other type of seal, which is designed to seal against the hole in the concrete wall, is forced into position in an existing hole.
The cast in-place connector seal requires that the manufacturer of manholes position the connector seal into the cast mold wall with a connector seal holding device prior to casting of the wall. This step insures that the connector seal's major diameter profile is cast in place and becomes an integral part of the concrete wall. There are several disadvantages, however, with this type of connector seal. First of all, the cast-in-place installation process is very time-consuming, since mechanical or pneumatic installation tools must be used on every connector seal cast in place. Secondly, the connector seal is dependent upon the casting process' concrete load pressure to insure that concrete flows all around the connector seal's major diameter profile, thereby creating a seal when dry.
Another disadvantage with this type of design is that by the seal becoming an integral part of the concrete wall, if the connector seal is damaged or defective, it cannot be removed, because with this cast concept the seal is not designed to be removable. This type of cast-in-place connector seal design is shown, for example, in U.S. Pat. No. 3,787,061.
As previously mentioned, the other type of connector seal which has traditionally been used in this field is designed to be forced into place into an existing hole. This type of seal utilizes a expansion split-ring with a major diameter arc length sized so that when the split-ring is mechanically expanded and clamped at a lock joint, it will form into a circle the circumference of which will compress the major diameter outer profile of the connector seal's elastomeric body against a concrete wall's receptacle hole surface. The disadvantage with this type of design is that the expansion rings require hydraulic or mechanical devices, as well as a significant amount of time and labor, to expand and lock the expansion ring in place. One example of such a connector seal/expansion ring is shown, for example, in U.S. Pat. No. 4,478,437.
A problem with known connector seals made of elastomeric material is the phenomenon of stress relaxation. That is, as mechanical forces deform the connector seal, the elastomeric body is exposed to stress. Eventually, the elastomeric material begins to relax under that stress and assume the deformed shape. This deformation results in a less efficient seal.
It is therefore the principal object of the present invention to provide an improved connector seal which can be inexpensively manufactured and easily installed.
It is another object of the present invention to provide a means of compensating for the stress relaxation property of the elastomeric material use in the manufacture of connector seals.
A further object of the present invention is to eliminate the time consumed by the cast-in-place process as well as the need for special installation equipment associated with known connector seals.
Still another object of the present invention is to provide an innovative new means of compressing a connector seal's major diameter outer sealing contact surface profile against a concrete wall's receptacle hole surface.